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The duodenum is a critical contributor to the regulation of food intake [17] and glycemic control. [18] As the first part of the small intestine, the duodenum is the initial site of nutrient absorption in the gastrointestinal tract.
The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about 5.5 metres (18 feet) long and folds ...
In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile, pancreatic juice and intestinal juice. The intestinal walls are lined with villi, and their epithelial cells are covered with numerous microvilli to improve the absorption of nutrients by increasing the surface area of the intestine ...
However, the primary function of the large intestine is water absorption from digested material (regulated by the hypothalamus) and the reabsorption of sodium and nutrients. [ 44 ] Beneficial intestinal bacteria compete with potentially harmful bacteria for space and "food", as the intestinal tract has limited resources.
Antibiotics can also cause villi, the little finger-like projections in the intestines that move things along, to lie flat, which can lead to problems with nutrient absorption, Wright adds.
This can cause vitamin deficiencies due to the improper absorption of nutrients in the small intestine. The small intestine can also be obstructed by a volvulus, a loop of intestine that becomes twisted enclosing its attached mesentery. This can cause mesenteric ischemia if severe enough. A common disorder of the bowel is diverticulitis.
In this way, the lining of the intestine is constantly renewed while the number of cells making up the epithelial layer remains constant. [5] In the small intestine, the mucosal layer is specially adapted to provide a large surface area in order to maximize the absorption of nutrients.
The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds.Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been previously digested by enzymes in the duodenum.